2003 LT-Z400 Idling/Acceleration Problem


Working on a buddies quad. 2003 Suzuki LT-Z400. Bike will start, but will not idle. You have to keep winging the throttle to keep the engine running. When you give it gas, it does not even want to rev up, it just makes a bogging noise, but still, doing this will keep it running. If you let off the gas, the motor dies instantly. While giving it gas, it is popping back through the exhaust (lean miss?). Once it gets warm, it will stall and will not re-start until it is cooled off.

I removed the carb, cleaned it thoroughly with carb cleaner & compressed air, but still the problem persists. I learned that if I remove the air cleaner, and block the majority of the air-flow through the carb, that it will idle, and will then rev up as normal. This indicates to me a LEAN condition. Since I have already been through the carb, and verified that all jets are clean & clear, I have no idea where to go from here. When the bike came to me, the vacuum line to the fuel pet-cock had been removed, and the nipple on the carb was just left unplugged. I have no idea how long it was operated this way. I did replace the hose, but the lean condition persists.

If anyone has an idea as to what I need to do to fix this-please let me know.. I am offering $20 (Pay-Pal, Check, or MO) to the person that offers the solution that fixes it. I have all the tools necessary for diagnosis and repair as I am an ASE tech at an auto repair facility. Please, any tips, or advise, you can offer will be tested to see if it will work.

A mojave i have was doing that.

It was due to trash getting into the bike. The connection from the Air intake was loose and was sucking up too much air.(and Trash with it)

but im pretty sure you checked that already.

Sosick, appreciate the fast response. Yes, I have verified that all of the connections between carb & motor are still pliable, with no cracks, and still sealing. I sprayed carb cleaner around the duct work while my co-worker was fighting to keep the engine running, and no change in RPM up or down.

Thanks for reading my rather long-winded post!

No problem, Just throwing out a possibility from experience.

Too bad i couldnt help you solve your problem.

The best of luck to you

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